// extern.cc
#include<iostream>
double warming = 0.3;
void update(double dt);
void local();
int main()
{
    using std::cout;
    cout<<"Global warming is "<<warming<<" degree\n";
    update(0.1);
    cout<<"Glocal warming is "<<warming<<" degree\n";
    local();
    cout<<"Global warming is "<<warming<<" degree\n";
    return 0;
}
